Primary cell



oct. 4, 1927.

h.. c v

PRIMARY CELL Filed Deo.

a i n M. L. MARTUS, ET *AL Patented Oct. 4, 1927.

UNITED STATES PATENT OFFICE.

MARTIN L. MARTUS, OF WOODBURY, AND EDMUND H. BECKER, F WATERBURY,

CONNECTICUT.

PRIMARY CELL.

Application filed December 29, 1926. ASerial No. 157,765.

This invention relates to primary cells; and it comprises a cell of the Lalande type having copper oxide opposed to zinc in a caustic alkali elect-rolyte, said cell containing .a a pre-shrunk body or mass of cellulose containin zinc compounds in contact with said electro yte; and it. further comprises a method of increasing the `open circuit life of such cells wherein cellulose is treated with a solution of alkali zincate and placed in contact with the electrolyte in such a cell; all as more fully hereinafter set forth and as claimed.

` Primary cells of the Lalande type having I5 a caustic alkali electrolyte, an electrode of zinc and an electrode of copper oxid, which also servesas a depolarizer, are in general use for all closed circuit purposes. For open circuit work, or any purpose where open 2" circuits occur for any length of time, they are not considered desirable. Their shelf loss is also serious. All these disadvantages depend upon the fact that copper oxid 1sI slightly soluble in solutionsof caustic soda and of caustic potash. Even with pure chemicals the solubility is suicient to be detrimental and in the presence of many organic impurities, the solubility is heightened. With the circuit closed, this solubility is unimportant, since the current keeps the electrolyte stripped. But in open circuit, after a time, copper in solution reaches the zinc and starts local action. This solution eect is, however, quite an uncertain one. The presence of all sorts of bodies influences it; many impurities heightening the solubility and therefore shortening the time during which the cell can safely stand in open circuit, while others have the converse effect. Among the latter is cotton or other form of cellulose. Cellulose in the presence of alkali tends to withdraw or absorb copper from solution. The active agent is really the alkali cellulose which is formed when the cotton comes into contact with the cell electrolyte. Cheese cloth and other fabrics are often used in these cells for structural reasons and they add to their utility in this respect the further function of 'giving the cell greater open circuit life.

We have found that cellulose treated with zinc oxid in the presence of alkali is a considerably more eflicient agent than alkali cellulose and forms a particularly efficient separator. As is well known, cotton fiber treated with alkali solution swells and Short ens; and a fabric becomes considerably denser in texture. We have found that by using sodium zincate in lieu of caustic soda, this effect is considerably accentuated; and 1n addition, the fiber takes up and holds a substantial amount of zinc oxidtby adsorption or chemical union, as the case may be. T he material so made we call, for Short, zinc cellulose. And we have found that a primary cell of the Lalande type containing amc cellulose in contact with the electrolyte 1s' much more resistant to open circuit conditions. Because of the conditions, it is a matter of considerable importance as toy how the zinc cellulose is located in the cell. Circulation and diffusion are slow in these cells and 1t is therefore best that the zinc cellulose voccur. in lines between the electrodes.

In most embodiments of our invention, we place layers of zinc cellulose ldirectl between the two electrodes. For examp e, in the structure of the prior patent to Martus, Ross & Becker, Patent 1,548,539, the sheet of cotton linters between the poles may be advantageously' replaced by a similar sheet of linters treated wit-h sodium zincate. In other types of cell, we treat cotton` batting with sodium zincate and dispose it inl the electrolyte .between the poles. In another way of embodying our invention, cheese cloth or similar fabric may be treated with sodium zincate and placed next one or other of the poles. In order to increase the quantity of zinc cellulose, it is often desirable to use in a cell both the loose material and the fabric; and this is done in the best embodiment of ourinvention now known to The sodium zincate solution used for treating the cotton or cloth may be made directly by dissolving'zincv or zinc oxid in caustic soda. Or old battery solutions may be used. This latter has the advantage of economy and these solutions are quite effec tive for our purposes. Dense solutions, going as high as 40 BaumeJ are desirable. Solutions of approximately 40 Baume may often be obtained from discharged cells of the Lalande type. On immersion of cotton or cloth in such a solution at the ordinary temperature, shrinkage quickly occurs. In the case of cheese cloth, the area. often decreases as much as 48 per cent; that is, a square of cheese cloth with sides of 100 v lande type cell using zinc cellulose. In this iti . advanta showing Fig.l 1 is .a cell partly cut away the interior,- and Fig. 2 is an enlarged view of a fabric diaphragm.

In the specific embodiment of our invention shown, element-1 is a cell container usly made of sheet iron andproto show vided wlth an opening 2 carrying an insui lanode 5. This zincis curved edges dis l zinc anodes as s lating bushing 3, through which conductor 4 passes to make 'contact with the zinc Y advantageousl amalgamated. Cathode 6 of copper oxi is disposed above and below the zinc anode and in Vcontact with the container 1,4 as shown.

lThe electrolyte, a solution of caustic soda having a concentration of 5to 20 per cent, is held and immobilized within the cell by ab` -sorption in a body of cotton linters or other absorbent form'of cellulose 7. The linters are previously treated with sodium zincate. Separators 8, made of wood or other form of cellulose, are-disposed between the clipper oxid cathodes and the zinc anode. ese are also preliminarily treated with sodium zincate.r The linters and the wood diaphragm together oier a considerable mass of kzinc cellulose effective in keeping the electrolyte stritpiped. In addition, we may, and usually o, employ layers 9 of paper or cheese cloth or other form of cellulose treated with zinc solution. In the embodiment shown, the partitions 9 are made of cheese cloth or paper formed in the shape of a broad U with their edges turned in as shown. They are placed -on each side of the separators 8, the twol innermost having their osed against the ends of the own and the edges of the two outermost being in contact with the copper oxid cathodes. This construction is such that these artition membersl are transverse y. to all lines etween. the twoelectrodes. Ter

trolyte, which comprises treating cellulose with asolution of sodium zincate havingva concentration of about 40, Baume.

2. The rocess of preparing a separating Y material or assembly and use in primary cells of the type'having a copper oxid cathode, a zinc anode and a caustic alkali electrolyte,l which comprises treating cellulose in sheet form with asolution of sodium zincate having a concentration of about 40 Baume.

'3. The process of reparing a separating material for assemb y ,and use in primary cells of the type having a copper-oxid cathode, a zinc anode and a caustic alkali electrolyte, which com rises treating cellulose with a solution of t e exhausted electrolyte frplm such a copper oxid cathode-zinc anode ce 4. The process of increasing the open circuit life of cellsof the Lalande type which comprises adding a body of pre-shrunk zinc cellulose to such a cell.

5.7111 the assembl of electrolytic cells having an alkaline e ectrolyte and zinc and copper oxid electrodes, that ste which comprises inserting in the electro yte and beF tween .the electrodes a partition formed of y cellulose that vhas been previously treated with a sodium vzincate solution.

6. In the assembly of electrolytic vcells I l having an alkaline electrolyte and opposed electrodes, that step which comprises inserting between the electrodes and inthe electrolyte a partition termedr of pre-shrunk zinc cellulose.

In witness whereof we have hereunto signed our names at Waterbury, Connecticut, this 28th day of December 1926.

MARTIN L. MARTUS. EDMUND H. BECKER. 

